The Vitamin D Window

When he examined the young lifeguard, he saw that almost every square inch of her body was well tanned. She had been wearing practically nothing when she worked at the beach.

Neil Binkley, M.D., told me about his patient because she had the highest physiologic level of vitamin D in her system of anyone he ever saw. Her level was 80 ng/ml.

I had to look up the word "physiologic" to make sure what Dr. Binkley meant. Physiologic in the sense that he's using it is "something that is normal, neither due to anything pathologic nor significant in terms of causing illness," according to a medical dictionary.

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Her level of 80 ng/ml is about the "maximum human physiologic level of vitamin D," he told me when I interviewed him yesterday. "And it doesn't make sense to push vitamin D beyond the physiologic level."

Dr. Binkley is now associate professor of medicine at the University of Wisconsin in Madison. The technical name for vitamin D in our systems is 25 hydroxyvitamin D. And Dr. Binkley is "an expert in the assays for 25 hydroxyvitamin D and how they can be applied clinically in the most accurate manner."

Stop at 80, Says Dr. Neil Binkley

He spoke yesterday morning to a general session of the annual meeting and clinical congress of the American Association of Clinical Endocrinologists in Houston. I'm in Houston to report on the AACE convention.

Dr. Binkley spoke on "Vitamin D -- Beyond Bone." After his speech, he gave a press briefing in the AACE's media room, where I caught up with him. I had the opportunity to talk with him before and after his briefing as well as question him during the briefing.

Like Dr. Binkley's lifeguard patient, the natural way for humans to get enough vitamin D is from exposure to the sun. That's one of three ways we can get vitamin D. The other ways are from supplements and from fortified foods.

I asked him if it wasn't safer to get the vitamin D level that we need from supplements. "Yes," he replied. "Vitamin D supplements don't give you skin cancer."

So what level of vitamin D do we need to reach? All of us need a vitamin D level of at least 40 ng/ml, he says. That's in line with the recommendations of GrassrootsHealth, which I wrote about here.

His level usually runs "in the 40s and 50s," he told me. To reach that level he takes 1,000 IU of vitamin D every day.

I have been taking 10,000 IU of vitamin D daily for the past couple of years. GrassRoots Health reported my total Vitamin D level as 83 ng/ml.

On the basis of the lifeguard's experience, Dr. Binkley says that my level is a bit too high -- a bit higher than normal. Still, he acknowledges that every quantitative test has variability.

"They are not perfect," he says. "Every quantitative test is done by a human being -- an imperfect entity -- using instrumentation that is also imperfect."

So if I cut back on my vitamin D supplementation, it will be only a little. Aside from having a level somewhat above normal, I have no reason to stop.

"I see no cost, because vitamin D is practically free," Dr. Binkley told me. "And I see no toxicity, because human physiology can crank us up to 60 or 70 or 80 [ng/ml]."

He says that he doesn't know what the toxic level is, whether it is 80, 100, or 200 ng/ml. "And the data aren't good," he continued. "But we have this fairly broad window of 40 to 80 ng/ml."

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Even though I get lots of sun on my hikes, the sun alone won't give me enough vitamin D. I have to take the vitamin D supplements because of my age. "Remember that the skin of old folks like you and me who have gray hair isn't quite as good as young skin," Dr. Binkley told me. "Young folks who are out and getting a lot of sun are telling us what human physiology can do."

Does that imply that us older folks should not have a level as high?

"No, I don't think so," he replied. "The fact that with advancing age we can't get our levels up to 80 with sun exposure doesn't make it right."

Dr. Binkley advocates vitamin D supplementation now. "But I think that the way to fix the problem of vitamin D inadequacy is not supplements," he told me. "I think it's food fortification."

Manufacturers now add vitamin D to few foods now. In addition, government regulations limit the amount in those foods. The government links those limits to the recommended intake. That has been set to a low level, but is currently under study.

In the meantime practically all of us need to boost our vitamin D level with those inexpensive little pills. I pay just 7 cents apiece for each 5,000 IU pill of vitamin D that I take.

It's inexpensive treatment and prevention for many conditions. Researchers have linked inadequate levels to several different health problems. Diabetes is one of them.

A recent study of "Diabetes and the Vitamin D Connection" relates vitamin D to both type 1 and type 2 diabetes. Vitamin D deficiency has been associated with increased risk of type 1 diabetes, the study says. Correcting a deficiency of Vitamin D also improves glycemic control and insulin resistance.

The window is open. While I may have to climb down a bit to get within it, most people need to climb up to the 40 ng/ml base. Those of us who have diabetes have especially good reasons to get within that window.